Distributor plate

ABSTRACT

A distributor plate ( 10 ) is shown for use in an impelling rotor of a vertical shaft impactor ( 14 ). Typically the impelling rotor is a chamber ( 12 ) arranged to rotate about a vertical axis A-A. Feed materials for breakage are gravity-fed into the rotating chamber ( 12 ). These materials strike the rotating distributor plate ( 10 ) which is located at the base of the rotor chamber ( 12 ). The plate has a substantially planar single-piece upper surface ( 24 ) onto which the feed materials are received. This substantially flat surface ( 24 ) facilitates rapid and easy expulsion of feed materials there across and out of the rotor chamber ( 12 ). The plate shown is a circular disc made of metal carbide. Use of a single-piece upper surface of the distributor plate ( 10 ) also will not result in the development of preferential wear sites at corners, edges, join lines etc, as can happen with the known distributor plates.

RELATED APPLICATION

This application claims priority from International Application No.PCT/AU2002/001446, filed Oct. 24, 2002, the disclosure of which isincorporated herein by reference in its entirety. The aboveInternational Application was published in the English language on May6, 2004, as PCT Publication WO 2004/037424.

FIELD OF THE INVENTION

The present invention relates to the components of an impactor apparatusfor breaking feed materials passed thereinto. In one form the inventionrelates to a feed distribution plate for use in a rotating shaftimpactor and will primarily be described with reference to this context.It should be remembered, however, that the components of the inventionhave broader use in feed distribution applications in all manner ofcrushing or breaking equipment.

BACKGROUND OF INVENTION

Impactors for breakage of materials are known in the art. Such apparatusincludes a rotating chamber arranged to rapidly rotate about an axis.Feed materials such as rock, gravel, mineral ores and the like arepassed into the rotor chamber via an inlet and contact a distributorplate located on one side of the chamber opposite to the feed materialinlet. The materials slide across the distributor plate and are ejectedsideways to impact against the surrounding walls of the impactor, andare thereby attritioned. The rotor chamber can become blocked when toomuch feed or feed containing large particles chokes the chamber,necessitating stopping of the apparatus. Due to the nature of the feedmaterials and the duty required of the apparatus, the distribution platesurface is normally made of a high strength alloy metal and this isusually an expensive item. In use the distribution plates are subjectedto significant and uneven wear.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a distributor plate foran impelling rotor of a rotating shaft impactor, where the impellingrotor is a chamber arranged in use to rotate about an axis and toradially eject material received therein through one or more ejectionports in a side wall of the chamber, the distributor plate being in useheld in a fixed position with respect to the impelling rotor, whereinthe distributor plate includes a body and a single wear element only,the single wear element being positioned on the body to alone cover anouter surface of the body onto which the material would otherwise bereceived. Such a wear element can reduce the severity of abrasive wearexperienced by the body due to the movement of material across thedistributor plate and thus prolong the time before replacement of theentire distributor plate is required. The use of a single wear elementalso prevents the development of preferential wear sites at corners,edges, join lines etc, which occurs with the known distribution platesthat have a two or more part surface.

Preferably the outer surface of the wear element is substantiallyplanar. A substantially flat surface facilitates rapid and easyexpulsion of material from the rotor chamber. The use of thesubstantially flat distributor plate ensures that the centre of therotor is less liable to blockage during use because the volume ofavailable space in the rotor chamber is large enough to allow an easierpassage of higher volumes of feed material, or feed materials which havea coarser overall particle size.

Preferably a surface of the wear element is affixed to a mating surfaceof the body. Most preferably the mating surface is substantially planar.

Preferably the wear element is a plate. Most preferably the wear elementis a circular disc.

Preferably the wear element is made of a wear resistant material.

Preferably the body includes a projection at its peripheral edge whichis used to locate the wear element on the body. Most preferably theprojection is a peripheral lip.

Preferably the wear element is spaced from the body by one or morespacers arranged between opposing mating surfaces of the body and thewear element so that, when the wear element is attached to the body byuse of an adhesive substance, the spacer(s) provide a predetermineddepth of the adhesive substance between the body and the wear element.The predetermined depth of an adhesive substance is typically theoptimum amount of adhesive recommended by the adhesive manufacturer.

Preferably one such spacer is a projecting ring on the body, concentricwith a central axis of the body and inset from the peripheral edge ofthe body.

Preferably a second peripheral edge of the body is bevelled in at leastone position, the bevelled edge adapted for the insertion of a leveringtool to facilitate movement of the distributor plate. Preferably theentire second peripheral edge is bevelled so that a levering tool suchas a screwdriver can be inserted in any location on the circumference tofacilitate lifting and grasping of the distributor plate by hand forrotation into a different wear position, or for servicing or replacemententirely.

In a second aspect the present invention provides a distributor platefor an impelling rotor of a rotating shaft impactor, the distributorplate including a wear element positioned on a body, the wear elementspaced from the body by one or more spacers arranged between facingsurfaces of the body and the wear element so that, when the element isattached to the body by use of an adhesive substance, the spacer(s)allow for a predetermined depth of the adhesive substance between thebody and the wear element.

In a third aspect the present invention provides a distributor plate foran impelling rotor of a rotating shaft impactor, where the impellingrotor is a chamber mountable via a coupling element to a shaft of theimpactor and arranged in use to rotate about an axis and to radiallyeject materials received therein through one or more ejection ports in aside wall of the chamber, wherein the distributor plate has a basalspigot, with a cavity in the spigot for receiving the coupling elementtherein in use. The cavity can be of any shape or dimension to suit theparticular requirements of a coupling bolt or any other fastening deviceused to attach the rotor chamber to the shaft.

In a fourth aspect the present invention provides a distributor platefor an impelling rotor of a rotating shaft impactor, where the impellingrotor is a chamber arranged in use to rotate about a rotating axis andto radially eject materials received therein through one or moreejection ports in a side wall of the chamber, wherein at least part of aperipheral edge of the distributor plate is bevelled for the insertionof a levering tool to facilitate movement of the distributor plate.

In a fifth aspect the present invention provides a distributor plate foran impelling rotor of a rotating shaft impactor, where the impellingrotor is a chamber arranged in use to rotate about a rotating axis andto radially eject materials received therein through one or moreejection ports in a side wall of the chamber, the distributor plateincluding a single wear element positioned on a body to alone cover anouter surface of the body and either of an opposing surface of the bodyor the wear element including a projection which locates the wearelement on the body.

Preferably the projection of the fifth aspect is located at the edge ofthe body and around its periphery. Most preferably the projection is anupwardly projecting circumferential lip or a partial circumferentiallip.

In a sixth aspect the present invention provides a mounting forsupporting a distributor plate in an impelling rotor of a rotating shaftimpactor, where the impelling rotor is a chamber arranged in use torotate about an axis and to radially eject materials received thereinthrough one or more ejection ports in a side wall of the chamber, thedistributor plate having a multi-sided basal spigot receivable in amulti-sided recess in the mounting, wherein the number of sides of therecess is a multiple greater than one of the number of sides of thespigot. It is therefore possible to move (rotate) the distributor platewith respect to the mounting into multiple “wear” positions to spreadthe abrasive wearing evenly over the distributor plate over time, ratherthan only having a limited number of grooves worn thereinto. Such afacility thus enables thinner wear plates to be used in such apparatuswhich reduces the unit cost and weight of the distributor plates.

Preferably the mounting is incorporated in a plate on which thedistributor plate rests.

Alternatively the mounting is incorporated in a rotatable shaft of therotating shaft impactor.

Preferably the recess of the sixth aspect is a twelve-pointed starshaped hole having twenty four sides and the basal spigot has six sides.

In a seventh aspect the present invention provides an impelling rotor ofa rotating shaft impactor including a distributor plate as defined inany one of the first five aspects.

In an eighth aspect the present invention provides an impelling rotor ofa rotating shaft impactor including a mounting as defined in the sixthaspect.

In a ninth aspect the present invention provides a rotating shaftimpactor including a distributor plate as defined in any one of thefirst five aspects.

In a tenth aspect the present invention provides a rotating shaftimpactor including a mounting as defined in the sixth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 shows an exploded partly sectioned side view of one embodiment ofa distributor plate for an impelling rotor of a vertical shaft impactorin accordance with the invention.

FIG. 2 shows a side view of the embodiment of FIG. 1 when assembled in avertical shaft impactor machine.

FIG. 3 shows an plan view of one embodiment of a distributor plate inaccordance with the invention.

FIG. 4 shows a sectioned side view of the embodiment of FIG. 3.

FIG. 4 a shows a detail of the embodiment of FIG. 4.

FIG. 5 shows an plan view of another embodiment of a distributor platein accordance with the invention.

FIG. 6 shows a sectioned side view of the embodiment of FIG. 3.

FIG. 6 a shows a detail of the embodiment of FIG. 6.

FIG. 7 shows a plan view of one embodiment of a support plate forsupporting a distributor plate of an impelling rotor of a vertical shaftimpactor in accordance with the invention.

FIG. 8 shows an exploded partly sectioned side view of one embodiment ofa distributor plate for an impelling rotor of a vertical shaft impactorin accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2 a distributor plate 10 is shown for use in animpelling rotor of a vertical shaft impactor 14. Typically the impellingrotor is a chamber 12 having a circular top plate 16 and a bottom plate18, with several support posts 20 located near the circumference of theplates 16, 18. The posts 20 join the top plate 16 to the bottom plate 18and space the plates 16, 18 apart. The rotor chamber 12 is arranged torotate about a vertical axis A-A (FIGS. 1 and 2).

In another embodiment of the invention the posts 20 can be replaced bydiscrete wall portions which have a generally elongate vertical andhorizontal dimension, the space between these walls defining portals inthe side wall of the chamber.

In the preferred embodiment shown, feed materials for breakage aregravity-fed into the rotating chamber 12 via an entry port 22 located inthe upper plate 16. Typical feed materials include rock, gravel, mineralores, metalliferous slags, glass and the like. These relatively coarsematerials pass into the rotor chamber 12 and contact or strike therotating distributor plate 10 which is located at the base of the rotorchamber 12. The materials slide across the distributor plate 10 and areejected radially out from the rotor chamber 12 through the spacesbetween the support posts 20, under centrifugal force. The materialsimpact the surrounding walls 21 of the impactor (or wall-mounted anvilsor other rocks located within the impactor walls 21) and are brokenapart or attritioned.

In further embodiments of the invention the axis of rotation of theimpelling rotor can be located on any angle from the vertical up to andincluding a horizontal axis. In any embodiment it is possible that thefeed materials can be passed into contact with the distributor plate by,for example, a pumping arrangement; the feed materials may therefore besuspended in a fluid, such as in a slurry, for example. Such a feedingarrangement may be more important in those embodiments of the inventionwhere gravity-feeding of the apparatus alone is not feasible.

In some embodiments of the invention the impelling rotor can be openended at the end which receives the feed materials and the “chamber”portion is generally defined as a region adjacent the distributor platewhich need not necessarily be enclosed by top and bottom plates. Forexample in “hammer and anvil” type impactors the distributor plate isusually held in position by a lower peripheral lip thereon which isinterlocked underneath several “hammer” elements of a wear resistantmaterial arranged around the perimeter of the distributor plate; in suchapparatus the hammer elements are not necessarily connected to anycircular top plate to define a rotor chamber.

In the present invention the distributor plate 10 is removeable forservicing, replacement etc. In one embodiment, the plate has asubstantially planar single-piece upper surface 24 onto which the feedmaterials are received. This substantially flat surface 24 facilitatesrapid and easy expulsion of feed materials from the rotor chamber 12. Ina plan view the flat surface 24 shown is circular, having a diametersubstantially equivalent to the width of the entry port 22. In furtherembodiments the distributor plate can be of a different diameter to thewidth of the entry port 22.

In known rotor devices the upper surface of the distributor plate iscommonly conical, or is sloped radially downwardly from a peak heightlocated at the centre of the distributor plate at the centreline A-A ofthe rotor. The centre of such distributor plates includes a hole forplacement of a centre bolt which fastens the distributor plate to therotor. In these known devices the distributor plate commonly has a twoor more part upper surface including a central conical portion and anannular peripheral portion joined to the central conical portion, withthe peripheral portion being more gently sloped radially outwardly thanthe conical portion. In such devices the conical portion is inserted forprotecting the centre bolt, the conical portion usually having an uppersurface which includes wear resistant materials.

The use of a substantially flat distributor plate 10 ensures that thecentre of the rotor is less liable to blockage during use because thevolume of available space in the rotor chamber is larger than that ofexisting devices. Such less obstructive geometry can allow an easierpassage of higher volumes of feed material, or feed materials which havea coarser overall particle size. Use of a single-piece upper surface ofthe distributor plate 10 also will not result in the development ofpreferential wear sites at corners, edges, join lines etc, as can happenwith the known distribution plates that have two or more parts whichform an upper surface thereof.

In the preferred embodiment the upper surface 24 of the distributorplate 10 is defined by a plate 26 formed from a material resistant towear and abrasion, such as a metal carbide, for example, tungstencarbide, or indeed a sprayed carbide or a hard ceramic. However, theupper surface 24 may also be treated to be hardened. In such an instancea special hardening process can be carried out on the distributor plateupper surface 24 before it is placed into service. The base portion 28of the distributor plate 10 is typically made of a less expensivematerial, such as mild steel, although other typical examples caninclude aluminium, brass, high density polyethylene, or other hardplastics. In the embodiment shown in the drawings, the metal carbidewear plate 26 is in the form of a thin circular disc which is positionedon and affixed to the upper surface of a thicker distributor plate baseportion 28. The wear plate 26 is positioned on the base portion 28 tocover an upper surface of the base portion 28 onto which feed materialwould otherwise be received during use of the apparatus, to reduce unduewear of the base material necessitating replacement of the entiredistributor plate 10.

When the term “substantially planar” is used in this specification it isbroadly defined to include surfaces which exhibit unavoidablemanufacturing irregularities or surface imperfections, scratches,spotting, minor ridges which can result from a metal forming process.

The wear plate 26 is located on the flat upper surface of the baseportion 28 by an upwardly projecting preferably circumferential lip 30which has a typical height of around 15-20% of the depth of the wearplate 26. In other embodiments the circumferential lip 30 may onlycomprise a partial circumferential lip, or perhaps only two or threeupwardly oriented protruding tabs spaced inset from and/or around theupper edge of the base portion etc. Similar projections may insteadextend downwardly from a lower surface of wear plate 26. Any type oflocating means is within the scope of the invention to retain the wearplate 26 on the upper surface of the base portion 28 of the distributorplate 10.

Further, the base portion 28 need not have a flat upper surface for thewear plate 26 to be seated thereon. For example, the base portion mayhave a slight conical shape (either convex or concave) to be mated witha corresponding shape on the underside of the wear plate. In any ofthese examples, the upper surface of the wear plate can still beprovided with a substantially planar or flat upper surface so that thedistributor plate has a substantially planar upper surface in use.

When mounting the wear plate 26 on the base portion 28 to formdistributor plate 10, the wear plate 26 is typically spaced from thebase portion 28 by a spacing means in the form of an upwardly orientedring 32 located on or formed at the upper surface of base portion 28.The ring 32 is concentric about the centre of the distribution plate 10located at the vertical axis A-A and is inset from the peripheral edge34 of the base portion 28. More than one ring can be employed on theupper surface of the base portion and typically the ring(s) are around0.5 mm in height. Ring 32 provides for a predetermined depth of anadhesive substance 33 which is used in the distributor disc assemblyprocess to join the base portion 28 and the wear plate 26, typically theoptimum amount of adhesive as recommended by the adhesive manufacturer.

In further embodiments of the invention the spacing ring(s) may onlycomprise a partial ring, or perhaps only several spaced apart upwardlyoriented surface projections (e.g. dimples) located on the upper surfaceof the base portion. Alternatively, the ring may be located on anunderside of the wear plate. Any type of spacer that provides apredetermined depth of an adhesive substance to retain the wear plate onthe upper surface of the base portion of the distributor plate is withinthe scope of the invention.

In embodiments of the invention where an adhesive substance is notrequired to join the wear plate to the distributor plate base portion,there is no requirement for there to be spacing rings (or any othersurface projections) on the upper surface of the base portion or on thelower surface of the wear plate. In such examples the wear plate can bespray-applied, welded, brazed or otherwise fused to the distributorplate base portion so that there is a direct bond between the adjacentsurfaces of the wear plate and the base portion.

Depending upon the diameter of the distributor plate and the thicknessof the wear plate, the distributor plate can be quite heavy andcumbersome to manipulate, requiring the use of a levering tool, orperhaps even a number of tools used simultaneously and spaced around theplate 10.

The lower peripheral edge of the base portion of the distributor plate10 is typically bevelled 36 in at least one position, so that a leveringtool such as a screwdriver can be inserted to facilitate lifting andgrasping of the distributor plate 10 by hand for rotation into adifferent wear position, or for servicing or replacement entirely. In apreferred embodiment the entire lower peripheral edge is bevelled.

Alternatively, a number of discrete bevelled portions in the lowermostperipheral edge of the distributor plate can be employed.

In a preferred embodiment the distributor plate 10 has a basal spigot 38provided with a downwardly facing cavity 40. The cavity is arranged toreceive a coupling bolt 42 therein when the plate 10 is mounted inchamber 12. The coupling bolt is used to fasten the bottom plate 18 ofthe chamber 12 (or other member linked to the bottom plate 18) to arotatable vertical shaft 44 of the vertical shaft impactor 14. Thecavity 40 in the spigot 38 can be of any shape or dimension to suit theparticular requirements of a coupling bolt 42 or any other fasteningdevice used to attach the chamber 12 to the shaft 44. In some exampleswhere the chamber 12 is fastened to the shaft by another fasteningarrangement other than a central coupling bolt, the cavity 40 in thespigot 38 may not be required to accommodate a fastening device and mayin fact be empty when in use. The spigot 38 can be of any suitable outershape, and in a preferred embodiment is a hexagonal prism shape.

Referring to FIGS. 3 to 4A and FIGS. 5 to 6A, where like referencenumerals are used to denote similar or like parts, it will be seen thatwear plates 26 and base portions 28 of varying thicknesses can beemployed. For example, a thinner distributor plate can be used for lessabrasive or lighter feed materials.

Referring in particular to FIGS. 1 and 7, a support plate 50 is used inthe vertical shaft impactor 14 to support the distributor plate 10. Thesupport plate has a multi-sided central recess 52 (in this case, athrough-hole) for the insertion thereinto of a multi-sided basal spigot38. The number of sides of the hole 52 in the support plate 50 istypically defined to be a multiple of the number of sides of the spigot38. In a preferred embodiment, the hole in the support plate is apolygon with, in effect, twenty four “sides” (being a twelve pointedstar shape). The basal spigot has six sides, and has a hexagonal prismshape.

In a preferred embodiment, where there are three posts 20 in theimpactor rotor chamber 12 (and therefore three spaces between thesupport posts 20 from which feed materials may be radially ejected fromthe spinning rotor chamber 12), it is possible to move (rotate) thedistributor plate 10 with respect to the support plate 50 into fourdifferent “wear” positions, to spread the abrasive wearing of the metalcarbide evenly over the wear plate 26 over time, rather than only havinga limited number of grooves worn into the wear plate 26. The number ofpossible wear positions can thus be determined by the number ofpolygonal corner points or star tips of the hole in the support plate Sodivided by the number of material outlet spaces from the rotor chamber12.

For example, in the instance where a six sided polygonal hole in thesupport plate receives a six sided basal spigot, in a chamber wherethere are three feed outlet spaces, the distributor plates is onlymoveable into two “wear” positions, which is rather limited. Havingpolygonal holes in the support plate of, say, 9, 12 or 15 sides meansthat, in a rotor chamber utilising three outlet spaces between supportposts, there are 3, 4 or 5 respective possible wear positions for thedistributor plate 10 to be moved into. It is also possible to producerotor chambers having 3, 4, 5 or even 6 outlet spaces.

FIG. 7 also shows a number of recessed bolt holes 54 in the supportplate 50 which are used to attach plate 50 via bolts 56 (FIG. 1) to aboss 58. Boss 58 is located to surround an upper end of the verticalshaft 44 on which the rotor body 12 sits (FIG. 1), and can also beattached to the base plate 18 of the rotor body 12 itself. The boss 58has a tapered hole 60 to match a corresponding taper on the verticalshaft 44. Any number, array or position of recessed bolt holes 54 forattaching the support plate to boss 58 is within the scope of thepresent invention.

In other embodiments the distributor plate can also be attached to anypart of the rotating impactor assembly including base 18 by the use ofbolts for receipt into corresponding holes in the base, or any otherjoining mechanism. Other joining plate types are within the scope of theinvention and the particular arrangements illustrated in FIG. 1 and FIG.7 are only one way of attaching the support plate and rotor body to therotatable shaft.

In still further preferred embodiments the distributor plate 10 can beattached directly to the shaft 44 of the rotor which rotates aboutvertical axis A-A. Referring to FIG. 8, where like reference numeralsare used to denote similar or like parts used in previous embodiments,the rotor shaft 44 itself can have a multi-sided central recess 80 forthe insertion thereinto of the multi-sided basal spigot 38 of thedistributor plate 10. Once again the number of sides of the recess 80 inthe shaft 44 is typically defined to be a multiple of the number ofsides of the spigot 38. In a preferred embodiment, the recess 80 in theshaft can be a polygon with, in effect, twenty four “sides” (being atwelve pointed star shape) to be used with a basal spigot 38 with sixsides, and of a hexagonal prism shape.

FIG. 8 also shows a number of recessed bolt holes 82 in the bottom plate18 which can be used to attach this plate via bolts 84 to a boss 86.Boss 86 is located to surround an upper end of the vertical shaft 44 onwhich the base plate 18 of the rotor body 12 sits. Any number, array orposition of recessed bolt holes 82 for receiving bolts 84 to attach thebase plate 18 to boss 86 is within the scope of the present invention.Furthermore the boss 86 can be attached to the vertical shaft 44 bymeans of a taper lock bearing 88 fitted about the shaft 44. Otherdevices for joining the boss to the shaft and the base plate of therotor body to the boss are within the scope of the invention and theparticular arrangements illustrated in FIG. 8 are only one preferredexample. In further embodiments, grub screws or external clips, forexample, can be used to join the component parts together.

In use the distributor plate can be moved into various wear positions(as held by the support plate or the rotor itself) by an operator tominimise the uneven nature of wear of the metal carbide wear plate 26.In turn such a facility enables thinner metal carbide wear plates to beused in such apparatus (see e.g. FIGS. 4, 4A and 6, 6A) which reducesthe unit cost and weight of the distributor plates. The use of adistributor plate with a basal spigot to “fasten” the distributor plateinto the rotor chamber 12 eliminates the need to have a central axialfastening bolt in the top of the distribution plate (an adverse featureof known apparatus, normally necessitating a conical or peaked cap ofmetal carbide being placed over the central fastening bolt after fittingduring use of the impactor rotor; uneven wearing due to some slightdislodgement of a prior art metal carbide cap, in addition to theblocking of the rotor chamber itself with feed materials, can commonlybe the result).

The performance and maintenance requirements of impactors are affectedby the cost of parts and how frequently they have to be changed. Areduced frequency of servicing and maintenance intervals combined withsafer and easier changing of machine parts and a lower consumption ofexpensive, wear resistant materials can lead to lower materials breakageor processing costs overall.

The materials of construction of the distributor plate and the supportplate can be any suitable materials which wear appropriately and thatcan be shaped, formed and fitted in the manners so described, such asthe appropriate metal, metal alloys, ceramics or plastics etc, referredto already. The support plate does not need to be especially hardened orbe made of very strong materials and can be formed from lighter weightmetals such as aluminium or hard plastics and the like.

It is to be understood that, if any prior art information is referred toherein, such reference does not constitute an admission that theinformation forms a part of the common general knowledge in the art, inAustralia or any other country.

Whilst the invention has been described with reference to preferredembodiments it should be appreciated that the invention can be embodiedin many other forms.

1. A distributor plate for an impelling rotor of a rotating shaftimpactor, where the impelling rotor is a chamber arranged in use torotate about an axis of a rotor shaft and to radially eject materialreceived therein through one or more ejection ports in a side wall ofthe chamber, the distributor plate being in use held in a fixed positionwith respect to the impelling rotor, wherein the distributor plateconsists of a single base portion including a central portion having asubstantially planar continuous upper surface and a single wear elementcomprising a substantially planar circular disc including a centralportion, the single wear element being positioned on and affixed to theupper surface to alone entirely cover the upper surface of the baseportion including the base portion central portion onto which thematerial would otherwise be received.
 2. A distributor plate as claimedin claim 1 wherein the wear element is made of a wear resistantmaterial.
 3. A distributor plate as claimed in claim 1 wherein the baseportion includes a projection at its peripheral edge which is used tolocate the wear element on the upper surface of the base portion.
 4. Adistributor plate as claimed in claim 3 wherein the projection is aperipheral lip.
 5. A distributor plate as claimed in claim 1 wherein thewear element is spaced from the base portion by one or more spacersarranged between the upper surface of the base portion and a matingsurface of the wear element so that, when the wear element is attachedto the base portion by use of an adhesive substance, the spacer(s)provide a predetermined depth of the adhesive substance between the baseportion and the wear element.
 6. A distributor plate as claimed in claim5 wherein one such spacer is a projecting ring on the base portion,concentric with a central axis of the base portion and inset from theperipheral edge of the base portion.
 7. A distributor plate as claimedin claim 1 wherein a lower peripheral edge of the base portion isbevelled in at least one position, the bevelled edge adapted for theinsertion of a levering tool to facilitate movement of the distributorplate.
 8. A distributor plate as claimed in claim 7 wherein the entirelower peripheral edge is bevelled.
 9. A distributor plate as claimed inclaim 1, wherein the upper surface of the base portion has a constantthickness throughout.
 10. A distributor plate as claimed in claim 1,wherein the base portion has a basal spigot provided with a downwardlyfacing cavity, the cavity being arranged to receive a coupling bolttherein when said plate is mounted in the chamber.
 11. A distributorplate as claimed in claim 1, wherein the base portion has a multi-sidedbasal spigot adapted for insertion into a multi-sided central recess ofthe rotor shaft.
 12. A distributor plate according to claim 11, whereina number of sides of said recess is a multiple of a number of sides ofsaid spigot.
 13. An impelling rotor of a rotating shaft impactorincluding a distributor plate for the impelling rotor, wherein theimpelling rotor is a chamber arranged in use to rotate about an axis ofa rotor shaft and to radially eject material received therein throughone or more ejection ports in a side wall of the chamber, thedistributor plate being held in a fixed position with respect to theimpelling rotor, wherein the distributor plate consists of a single baseportion including a central portion having a substantially planarcontinuous upper surface and a single wear element comprising asubstantially planar circular disc including a central portion, thesingle wear element being positioned and affixed to the base portion toalone entirely cover the upper surface of the base portion including thebase portion central portion onto which the material would otherwise bereceived.
 14. A rotating shaft impactor including a distributor platefor the impelling rotor, wherein the impelling rotor is a chamberarranged in use to rotate about an axis of a rotor shaft and to radiallyeject material received therein through one or more ejection ports in aside wall of the chamber, the distributor plate being held in a fixedposition with respect to the impelling rotor, wherein the distributorplate consists of a single base portion including a central portionhaving a substantially planar continuous upper surface and a single wearelement comprising a substantially planar circular disc including acentral portion, the single wear element being positioned and affixed toalone entirely cover the upper surface of the base portion including thebase portion central portion onto which the material would otherwise bereceived.